Low Frequency Hydrophone

A low frequency hydrophone is notoriously difficult to calibrate. A world-leading technological solution resulted from a unique collaborative partnership between Rainhouse Manufacturing Canada Ltd. and Ocean Networks Canada.

Project overview

Project name: Calibration system low frequency digital hydrophone
Product name: Hydrophone calibrator (up to 410 bar)
Client: Ocean Networks Canada Innovation Centre
Type of project: Collaborative design
Industry: Marine
Contract awarded: May 2013
Product delivered: November 2013
Location: Victoria, B.C.

Rainhouse Manufacturing Canada Ltd.’s engineering support and manufacturing capability resulted in project success

Low frequency smart hydrophones, such as the Ocean Sonics icListen LF, have opened the door to the use of hydrophones for earthquake and underwater landslide studies. These hydrophones have also dramatically improved market use of low frequency hydrophones to study large baleen whales and low frequency shipping noise in the deep ocean.


While the sensors are excellent, there was no way to accurately calibrate the hydrophone sensitivity at frequencies from 20 Hz down to 20 mHz, which reduced the effectiveness of the data.

Ocean Networks Canada (ONC), a University of Victoria initiative, operates a series of large and small ocean-observing networks. These networks are located on Canada’s West Coast and at Cambridge Bay in the Canadian Arctic. The Innovation Centre is the ONC’s business development arm and operates the Technology Demonstration Facility. This facility helps ocean-instrumentation manufacturers develop, test, and demonstrate new technologies for oceanography.

The Innovation Centre took up the challenge and devised a concept and feasibility prototype for a very low frequency digital hydrophone calibration system. However, ONC did not have the equipment or expertise required to develop and produce such a sophisticated, laboratory-grade calibration system and have it pass provincial pressure vessel certification. Additional expertise was needed, and Rainhouse Manufacturing Canada Ltd. provided it.


Rainhouse’s excellent reputation for designing and fabricating complex, unique systems for a wide variety of industries made them the preferred partner for the project. The Rainhouse team embraced the challenge and became a second driving force for the development of this new technology.

While maintaining a close collaboration with the Innovation Centre scientists and engineers, the Rainhouse team took the concept and designed a functional system. The process included several solid model iterations, design simulation, fabrication, testing, and provincial boiler certification. Rainhouse was also instrumental in producing the patent documentation.


After delivery, Rainhouse Manufacturing Canada Ltd. worked with the Innovation Centre to further refine the system. Thanks to the new technology, hydrophone calibrations were being performed at frequencies and accuracies never before achieved.

To date, the system has been used for more than 27 very low-frequency hydrophone calibrations by ONC observatories, Natural Resources Canada, Cetacea Lab, Orca Lab, SIMRES, Ocean Sonics in Nova Scotia, and Saab’s torpedo test range in Sweden. Four other facilities have requested similar calibration systems.